Study On Screening And Characteristics Of Organophosphorus Pesticides Degradation Bacteria

Organophosphate pesticides are higher efficiency, lower residue, and they ensured to increase production when long-term and widely used, while as the environment pollution caused by them could not be neglected. Degradation by microorganism have many advantages such as higher efficiency, lower cost, no secondary pollution and complete degradation, and it is one of the best way to bioremediate the pollution soils.In this study some strains were isolated from the polluted soils sampled respectively from Sanonda pesticide factory in Shashi, cotton fields in Huanggang and farmland in Jingzhou. These strains could degrade organophosphate pesticides such as methamidophos and methyl parathion. The strain HS-A32 capable of degrading methamidophos and HS-D38 capable of degrading methyl parathion were selected and the preliminary study including physiological and biochemical characters, 16S rDNA identification, their degradation characteristics were carried out. The quantitive and qualitative research of MAP degradation by HS-A32 strain were processed by thin layer chromatography (TLC) with DNS-Cl and High Performance Liquid Chromatography (HPLC). The results indicated that HS-A32 could use methamidophos as the sole carbon and nitrogen source. The rate of degrading MAP was up to 86% within 3 days in the conditions of 30℃, 150 rpm shaking, and 500 mg/L MAP. The efficiency of MAP degradation was increased by adding available carbon and nitrogen source. NH₄⁺ can be detected by thin layer chromatography (TLC) with DNS-Cl. This result showed the degradation enzyme borned by HS-A32 could break the P-N chemical bond and gained nitrogen source for growth. The characteristics of HS-A32 were investigated including 16S rDNA amplification, sequencing, and blast analysis. The phylogenetic tree of HS-A32 was constructed by PHYLIP software. These results of physiological and biochemical tests indicated that HS-A32 belongs to Acinetobacter. HS-A32 strain could also degrade other organophosphate pesticides such as triazophos, methyl parathion, phoxime, dichlovo, and it is a bacterium with high efficiency and broad-spectrum ability of degradation organophosphate pesticides.The bacterium HS-D38 could use methyl parathion as the sole carbon and nitrogen source. The optimum conditions for HS-D38 growth were 35℃of temperature, pH 7.0, 200 mg/L MP concentration, and MP tolerance concentration was up to 800 mg/L. The results of dynamic scanning and thin layer chromatography with DNS-Cl indicated that HS-D38 could degrade p-nitrophenol in the course of degrading methyl parathion, and it could absolutely degrade methyl parathion. The characteristics including biochemistry characteristic and 16S rDNA phylogenetic analysis indicated that HS-D38 belonged to Pseudomonas aeruginosa. Substance applied tests showed several kinds of carbon and nitrogen source could be used by HS-D38, and p-nitropbenol could be used as the sole carbon and nitrogen source. The strain could degrade aromatic compound such as phenol and p-benzenediol but could not degrade to benzene, 1, 3-benzenediol and 2, 4-dinitrophenol. Plasmid of HS-D38 was cured treated by different concentration of SDS and acridine orange (AO) in order to determine the coding-site of degradation enzyme. Plasmid-cured strain of HS-D38 could not degrade MP and PNP showed that degradation enzymes were bomed in plasmid.